Apparatus for forging crankshafts and the like

ABSTRACT

Improvement in apparatus for forging crankshafts and like workpieces. This improvement is characterized in that an upper crankpin die is mounted on a piston movable in relation to an upper cross member which is actuated by the ram of a forging press, said piston being responsive to a hydraulic ram having its cylinder carried by said cross member. The pressure developed in said ram is adjustable by means of a discharge valve set according to the dimensions of the workpiece to be forged, said valve permitting of performing the forging operation in two steps, i.e., firstly upsetting the metal while offsetting the crankpin, then forging the crankshaft webs at the end of the upsetting step.

United States Patent Ruget [451 Mar. 21, 1972 541 APPARATUS FOR FORGlNG2,534,613 12/1950 Meley ..29/6 CRANKSHAFTS AND H LIKE 2,747,253 5/1956Conchon ..29/6

[72] inventor: Gabriel Ruget, St. Etienne (Loire), France v FOREIGN EN0R APPLICATI NS [73] Assignee: Compagnie Des Ateliers et Forges de La757,526 9/l956 Great Britain ..29/6

Loire (St. Chamond-Firmidy-St. Etienne- J co -ll z Rochefoucauld riPrimary Examiner-Charles w. Lanham France Assistant Examiner-Michael J.Keenan 22 Filed; July 14 19 9 Attorney-Wenderoth, Lind & Ponack [21]App], No.: 84l,272 Q [30! Foreign Application Priority Data improvementin apparatus for forging crankshafts and like July I). I968 France ..l59, 915 I workpieces 'Fnpmvemem ls cpamctemed Feb. 24. I969 France ..6904 677 upper crankpm die mounted on a piston movable m relation -10 anupper cross member which is actuated by the ram of a 52 us. Cl ..72/412,72/472, 29/6 forging press, said Piswh being responsive to a hydraulicram [51 1 Int. Cl.'.., B21d 37/00 having its cylinder carried by saidcross member. The pressure [58] Field of Search ..29/6; 72/412, 471, 472developed in said ram is adjustable by means of a discharge valve setaccording to the dimensions of the workpiece to be [5 1 Rflefences Citedforged, said valve permitting of performing the forging operation intwo, steps, i.e., firstly upsetting the metal while off- UNITED STATESPATENTS setting the crankpin, then forging the crankshaft webs at the2,827,685 3/1958 Cleghorn ..29/6 end of the upsetting step. 2,790,2274/1957 Fine "29/6 3 Claims, 13 Drawing Figures mammal 1972 3,650,143

' sum 1 0F 9 GABRIEL RUGET, Inventor Attorneys PATENTEUMARZ] m2 SHEET 3BF '9 1 man L I PAIENTEUMAHm 1972 SHEET 4- UF 9 Had GABRIEL RUGET,Invantor PAIENIEnmm 1972 3,650,143

sum 5 OF 9 GABRIEL RUGET, Inventor ald/14M Attorneys PATENTEDMARZ] I9723,55 4

SHEET7UF9 GABRIEL RUGIJT, Inventor AtEarnc-ys PATENTEUMARZI m2 SHEET 8[1F 9 W\ M Q Q GABRIEL RUGET Inventor [1M4 KMM Attorneys PATENTEDMAR211972 SHEET. 9 or 9 Calibrated disc/var a valve /7; E

P/rcssure f/uiaL Disfribu! or H" 1,. caliEr-a ad discharge valveflistribu [0r Low-pressure calibrated discharge valve Return Pressurefluid GABRIEL Rum-y Inventor Attorneys APPARATUS FOR FORGING CRANKSHAFTSAND THE LIKE The present invention relates to apparatus for forgingparts characterized by considerable variations in their cross-sectionaldimensions, as described in the British Pat. Nos. 622,938, 628,519 and696,618.

These apparatuses are adapted to be used in conventional forging pressesand their chief purpose is the direct forging of crankshafts withouttwisting of the material. The blanks thus forged are provided with acontinuous grain flow, for the necking operation, which is necessary inthe usual method of slab forging, is eliminated and the metal fibers aredirected parallel to the outer surface of the workpiece. The peripheralzone where the metal displays better properties remains in the vicinityof the surface, thus reducing appreciably surface defects, and the axialzone of the initial blank remains in the vicinity of the neutral axis ofthe finished throw and does not come to the surface at the junctionbetween the crankpins (or journals) and the webs or cheeks, i.e., wherethe throw is weakest and highly stressed. With this specific texture,stresses are always directed longitudinally of the metal grain flow andthe fatigue strength of the workpieces thus obtained is increasedconsiderably.

This result is obtained by using an apparatus of the type showndiagrammatically in FIG. I of the attached drawing, this apparatuscomprising essentially a lower bed plate 1 supported by the fixed crossmember 2 of a conventional forging press;

a pair of sliding cradles 3 and 3 supported by slideways 4 and 4 carriedin turn by said support 1, and

an upper cross member 5 rigid with the upper crosshead 6 of the press.

In crankshaft forging, the initial blank comprises as a ruleenlargements or swellings separated by constrictions. The enlargementsgenerally are to constitute the webs or flanges of the forgedcrankshaft, i.e., the portions of which the shape is altered, and theconstrictions are to constitute the necks of the forging, whethereccentric or not.

When following the press action the upper cross member 5 is lowered itcauses via the inclined slideways 7, 7' the cradles 3 and 3' to movetowards each other. This movement induces the upsetting of the metal oneach side of the intermediate portion between the two end dies closed bythe pressure of rams 9 and 9 enclosed in the upper cross member 5.

As the cradles 3 and 3" are moved towards each other the upper crossmember 5 pushes vertically downward the upper crankpin die '10 againstthe lower crankpin die 11 which is supported by another ram l2, so as toset off transversely and downwards the upset metal.

These forging apparatuses transform the vertical movement of translationof the upper cross member 5 of the press into two perpendicularmovements combined together in order to forge a throw on the blank. InFIG. 1 there is shown in dash and dot lines, between the two cradles 3and 3', the lower crankpin die 11 and the upper crankpin die 10, a throwformed at the end of the forging operation.

It is also possible to forge crankshafts from plain bars, i.e., withoutalternate swellings and constrictions, by using the arrangementdescribed and illustrated in the British Pat. No. 628,519. In this case,the cross member 5 engages firstly the cradles 3 and 3 via slideways 7and 7, thus producing a first upsetting of the blank metal; then thiscross member 5 moves downward the upper crankpin die and the actualforging operation as described hereinabove begins at that time. Thispreliminary upsetting permits, from an initial plain bar, of disposingof a quantity of metal sufficient for giving to each web the necessaryvolume and this arrangement is particularly advantageous in the forgingof crankshafts having relatively large webs in proportion to the journaldiameter.

The British Pat. No. 696,618 describes the use of auxiliary cylinder andpiston units acting upon the cradles 3 and 3' for increasing theupsetting force available and this arrangement is extremely advantageouswhen it is contemplatedto use a press of relatively long useful strokebut limited tonnage.

LII

It may be emphasized that all these arrangements have two commonfeatures: in fact, on the one hand as the upper crankpin die 10 is rigidwith the cross member 5 theupsetting and offsetting strokes terminate atthe same time, so that it is not possible to stop one stroke before theother; on the other hand, the metal constituting the webs is shapedfreely," i.e., without being enclosed in a die or like element duringany phase of the forging operation.

The advantageous features characterizing these auxiliary forgingapparatuses are obvious and the crankshafts forged therein are of higherquality since the metal grain flow is properly oriented and at a lowercost, since the metal loss and machining time are reduced. However, thisforging process produces rough-forged webs having substantially theshape of a plate of which the section through a plane perpendicular tothe initial axis of the blank bar is of oval configuration,substantially an ellipse of very reduced eccentricity. In this case theupsetting length and the diameter of the initial bar must be calculatedwith a view to permit the inscription of the web to be machined withinthis ellipsoid, so that irregular and frequently considerable extrametal thickness must be provided thus increasing the machining timeaccordingly.

To reduce the total cost of crankshafts while increasing the efficiencyof these forming apparatus, reduced and regular machining allowancesmust be obtained in the resulting blank. Under these conditions, themetal flow must be reduced by causing upper and lower crankpin dies andcradles to form together, at the end of the forging stroke, a closedvolume similar to a die which the metal is forced to fill up. Thisimprovement makes known apparatuses capable of utilizing these dies byexploiting more completely the tonnage of the press. In fact, the chiefdifficulty lies in the fullest or better utilization of the press poweroutput and experience teaches that the forces to be implemented forobtaining a satisfactory forging operation are extremely high andincrease as the shape contemplated departs from the shape that would beobtained if the metal was allowed to expand or flow freely." This effectis evidenced by a comparison between FIGS. 2 and 3 of the drawing.

In the case illustrated in FIG. 2, the metal flows freely and theupsetting force is proportional to the surface area of the meridianplane of the web and also to the creep strength of the metal. This creepstrength increases as the e/D ratio decreases. Therefore, two causes actsimultaneously to increase the upsetting force at the end of the stroke.

In the other case (FIG. 3) the metal flow is limited by theconfiguration given to upper crankpin die 10 and lower crankpin die 11.Assuming that the dimension D is the same as in the case illustrated inFIG. 2. On the other hand, as the metal contacts partly the upper andlower crankpin dies, the'ratio e/D should no more be used fordetermining the flow limit, the latter being subordinate to the sum ofboth ratios e /D e /D, since the meta] shape is no more altered in thearea already in contact with the sidewalls; thus, the flow limit isconsiderably higher and increases to very important proportions when :2and 2 tends to approach zero.

The upsetting force to be used when forging metal is about six time thatnecessary when the metal is allowed to flow freely, and increases veryconsiderably during the last portion of the stroke.

A similar line or argument may be followed for explaining the incrementin the offsetting effort at the end of the stroke. In fact, theshear-stress creep strength is lower in the planes remote from thegeometrical bases than in the vicinity thereof; as these bases arecloser to each other the flow limit and therefore the offsetting effortincrease.

But if the metal is forged, two factors add their effects: on the onehand the creep strength is increased for the process takes place asifthe bases were spaced by a distance e e in Finally, a third cause iseffective in a forging operation; when the metal is forged in a die,some kind of escape or burr must be provided for the forged 'material,to permit the regularization of the shapes and stresses implemented. Themetal burr thus formed has a considerable surface in proportion to itsvolume; besides, it cools very rapidly and its malleability isconsiderably lower. To shear this burr, very important forces must bedeveloped at the end of the forging stroke.

All these reasons account for the fact that hitherto known forgingapparatuses are ill-suited for properly forging the metal; as theupsetting and offsetting operations are performed simultaneously, themaximum forces are added. At the beginning of the stroke, the forceavailable is considerably in excess of the reaction force, and-at theend of the forging operation the antagonistic efforts become abnormallyhigh and cannot be overcome. I

It is a first object of this invention to make the best possible use ofthe power available in the forging press by modifying the upper crankpindie control system.

This first object is obtained by eliminating the hitherto customaryrigid coupling between the movable cross member and the upper crankpindie so that the synchronization between the offsetting and upsettingmovements ceases when the offsetting movement is ended but a shortupsetting stroke is still available. 1

This invention is characterized in that the upper crankpin die isrendered independent of the upper cross member by mounting said uppercrankpin die on a piston movable in relation to said cross member, saidpiston being controlled by a hydraulic ram having the pressure in itscylinder regulated by a discharge valve preset as a function ofthedimensions of the piece to be forged, said valve permitting ofperforming the forging operation in two phases: firstly, upsetting themetal while offsetting the crankpin, then forging the webs during a lastupsetting phase.

According to a modified form of embodiment, the pressure in saidhydraulic cylinder is adjustable by means of a pair of discharge valvesto permit in succession a preliminary upsetting, continuing thisupsetting in conjunction with the crankpin offsetting,,and finallyforging the web during a last upsetting phase.

According to another feature characterizing this invention, the actionexerted by the rams clamping the lateral holding blocks or die holdersof prior machines of this character is replaced by the verticalcomponent of the force transmitted FIG. 4 illustrates the forgingapparatus in longitudinal vertiby inclined slideways formed on the uppercross member of.

the apparatus to other slideways rigid with upper holding blocks.

It is a complementary object of this invention to combine the forgingoperation imparting'an elliptic configuration to the crankshaft webswith a final forging operation aiming at giving a well-defined shape tothese webs. This double operation will be referred to asclosed-die-forging" in the following disclosure.

These objects are carried out by providing dies disposed: either on thelower and upper lateral holding blocks or die holders; either on theupper and lower crankpin dies;

either on the upper crankpin die and on the lower lateral holding blocksor die holders;

or on the lower crankpin die and on the upper lateral holding blocks ordie holders.

Other features and advantages of this inventionwill appear as thefollowing description proceeds with reference to the accompanyingdrawing illustrating diagrammatically by way of example typical forms ofembodiment of the invention. In the drawings:

FIG. 1 is a schematic view illustrating a forging apparatus as used inthe prior art.

F IG. 2 is a schematic view illustrating a metal blank where the metalflows freely."

FIG. 3 is a similar view showing how the metal flow is limited by theconfiguration given to the upper crankpin die and the lower crankpindie.

cal section through the plane of symmetry containing the axis of theblank to be forged, this apparatus being similar to the one disclosedand illustrated in the British Pat. Nos. 622,938 and 696,618 butincorporating in addition the following two features characterizing thisinvention: firstly, the upper crankpin die carried by the upper crossmember is rigid with a piston movable in relation to said cross memberin the cylinder provided in said cross member, whereby the off settingmovement is completed when a short final upsetting stroke is stillavailable; secondly, impressions are formed in said upper crankpin dieand on the lower crankpin die constituting, with the forging faces ofthe lateral holding blocks or die holders, the web dies. In theseFigures, the same parts are designated by the same reference numerals asin FIG. 1;

FIG. 5 is a detail sectional view showing a die member arrangement;

. FIG. 6 is an elevational view showing a crankshaft obtainable by usingthe die members illustrated in FIG. 5;

FIGS. 7 and 8 are detail sectional views showing two other die memberarrangements;

FIG. 9 is a diagram showing the action exerted by an inclined slidewayof the upper cross member on an inclined slideway of the correspondingcradle;

FIGS. 10 and 11 are longitudinal sectional views showing the forgingmachine incorporating features already illustrated in FIG. 4 as well asother features to be described hereinafter.

FIG. 12 is a diagram illustrating the hydraulic circuit according to thefeature of this invention whereby the pressure developing inthe uppercrankpin die ram is adjusted by a calibrated discharge valve;

FIG. 13 is a hydraulic circuit diagram according to the modified form ofembodiment whereby the pressure in the ram is adjusted by means of twodifferently calibrated valves.

As illustrated in FIG. 4, the cradles 3 and 3 carry holding blocks 14and l5, l6 and 17 adapted to hold the blank in position during theforging operation. The faces of these holding blocks which register withthe forging zone are flat and the upper crankpin die 10 and the lowercrankpin die 11 have formed therein the impressions 20 and 22, 19 and21. At the end of theshaping operation the holding blocks are stopped byagainst the fiat side faces of theupper and lower crankpin dies so thaton either side of these two members a pair of closed dies are formed forshaping the blank metal to the desired configuration.

' According to the modified form of embodiment illustrated, in FIG. 5,the dies may be hollowed out of the lateral'holding blocks. Thus, asshown in this Figure, dies 31 and 33 are formed in the lateral blocks 15and 17 for the pair of upper impressions, and other dies 30 and 32 areformed in the lateral blocks 14 and 16 for the pair of lowerimpressions.

This arrangement is advantageous in the very frequent cases ofcrankshafts 35 having webs 34 formed with a bevel 36 as illustrated inFIG. 6.

Other arrangements may be obtained by combining the two arrangementsillustrated in FIGS. 4 and 5, thus:

FIG. 7 illustrates impressions 20 and 22 formed in the upper crankpindie 10, and other impressions 30 and 32 formed in the lower lateralblocks 14 and 16, respectively;

FIG. 8 shows impressions l9 and 21 formed in the lower crankpin die 11,and other impressions 31 and 33 formed in the upper lateral holdingblocks 15 and 17, respectively.

According to the geometrical arrangement of the crankshaft webs, andalso the length and diameter of the crankpins and journals, one or theother of these solutions may be adopted.

Instead of being integral with the cross member 5 as in hitherto knownconstructions, the upper crankpin die 10 is carried by a piston 13aslidably mounted in the cylinder 13 of a hydraulic ram. The latter maybe supplied with fluid under pressure when the cross member 5 is in itsuppermost position, and when this member 5 moves downwards the cylindermay be connected to a fluid reservoir (not shown) via a valve adjustedto open under a predetermined pressure adjustable however as a functionof the dimensions of the crankshaft to be forged.

The diagram of the hydraulic device connected to the ram 13 isillustrated in FIG. 12. This device comprises a calibrated dischargevalve 70 connected to the ram 13, and a distributor 71 receiving thepressure fluid, the return taking place to the reservoir 72.

Similarly, the lower crankpin die 11 is carried by a piston 12a movablein a cylinder 12 of a hydraulic ram supplied with fluid under pressurewhen the movable cross member is in its uppermost position, just beforethe forging operation begins, said cylinder being connected to thereservoir via an adjustable valve when the cross member 5 is movingdownwards.

The advantageous features characterizing this apparatus will appear moreclearly as the description of its mode of operation proceeds.

The blank 8, of which the portion to be shaped into a throw has justbeen heated to the proper forging temperature, is laid with the properorientation upon the holding blocks 14 and 16 integral with the cradles3 and 3 Preferably, the lower assembly of the apparatus should beshifted laterally so that it lies outside the press during the handlingoperation. This operation comprises two steps: firstly lowering theblank with a crane by a vertical movement of translation upon theholding blocks, then introducing this complete lower assembly into thepress by a movement of translation parallel to the blank axis and underthe control of the sliding table normally equipping the forging press.

When the press is actuated, the upper crosshead 6 is lowered as well asthe upper cross member 5, whereby its inclined slideways 7 and 7' engagethe registering slideways formed on the sliding cradles. At the sametime the upper tool members engage the lower tool members, thus causingeach one of the two blank portions clamped between the blocks 14 and 15or 16 and 17 to become integral with the sliding cradle 3 or 3' in whichit lies. As the cross member 5 continues its downward stroke, theforging operation proper begins.

The inclined slideways and the auxiliary hydraulic actuators l8 and 18'move the sliding cradles towards the upper crankpin die 10, thusupsetting the blank metal. At the same time the offsetting of the blankportion constituting the crankpin of the throw being shaped begins. Infact, due to the operation of the discharge or exhaust valves of rams 12and 13, the lower crankpin die exerts an upward force F] and the uppercrankpin die exerts a downward force F2. These valves are so adjustedthat the force F| corresponds to the clamping force to be applied to thecrankpin, and the force F2 is slightly superior to the sum of the forceFr, of the offsetting force and of the opening force of the centralholding blocks which is caused by the pressure exerted by the metalagainst the lateral walls of impressions 20 and 22.

Under these conditions, when the cross member 5 is lowered the piston12a supporting the lower crankpin die 11 recedes in cylinder 12 and thepiston 13a supporting the upper crankpin die 10 is stationary withrespect to the upper cross member 5. Thus, the crankpin die is offsetdownwards. Then as the upsetting movement continues the lower crankpindie 11, after having been lowered through a distance corresponding tothe radius or throw of the crank to be obtained, engages stop members(not shown), thus stopping the piston movement. The offsetting is thencompleted and about the three fourths of the upsetting or forging strokeare performed. The press has thus supplied the accrued efforts necessaryfor the beginning of the upsetting phase and the whole of the offsettingoperation. As the latter takes place without enclosing the metal in thedie members, the offsetting force increases with the stroke but remainsrelatively moderate.

From this moment, on the upper crankpin die 10 is in abutment and thepressure in the cylinder 13 controlling the upper crankpin 10 risesuntil the exhaust valve controls the discharge of the hydraulic fluid.During the remaining portion of the crosshead stroke the thrust suppliedby the press is equal to its rated thrust minus the force F This is thethrust available, accrued by the force of rams 18 and 18' for completingthe upsetting and forcing the metal into the shaping impressions of thedie members. During this second phase the only movement taking place isthe upsetting of the metal which is terminated when the holding blocks14,15 and 16,17 stop against the upper crankpin die 10 and lowercrankpin die 1 1. Then the crankthrow forging operation is completed.The press ram 6 is raised and carries along the cross member 5 and theupper tool members, and when these members have reached their uppermostlevel, the lower assembly of the forging apparatus can be removed fromthe working table or bed of the press. The blank is subsequently removedfrom the holding blocks, and the sliding cradles 3 and 3' are restoredto their initial position; then the rams 13 and 12 are supplied withpressure fluid to similarly restore the upper and lower crankpin dies totheir initial positions, and a new cycle can be resumed by introducing afresh blank with a vertical movement of translation. In certain casesthis blank may be introduced into the apparatus without removing thelower portion of this apparatus from under the press crosshead; in thiscase a vertical movement of translation directed at right angles to theblank axis must be combined with a successive horizontal movement oftranslation parallel to this axis. Thus, time can be saved for forgingthrows at the ends of the bars.

From the above description and from the details of the operation of theapparatus according to this invention it will be seen that it ispossible to forge crankshaft webs by making a better use of the thrustproduced by a forging press.

A modified form of embodiment consists in communicating the cylinder 13with the reservoir via two discharge valves.

The diagram of the hydraulic device according to this modified form ofembodiment is illustrated in FIG. 13. It comprises a high-pressurecalibrated discharge valve 73 and a lowpressure calibrated dischargevalve 74, and a pair of distributors 75, 76.

The first valve is directed to exert a vertical downward force upon theupper crankpin die 10, this force being veryslight ly inferior to Fr(the crankpin clamping force). This first valve is closed by thedownward movement of the upper cross member and under these conditionsthe ram 13 can be discharged through the other valve setting a pressurevalue corresponding to the force F2. The crank forging process takesplace in three successive steps. During the first step the uppercrankpin die cannot overcome the lower crankpin die force and the metalis simply upset until the first discharge valve is closed; the secondand third steps follow as described hereinabove. This sequence ofoperations: preliminary upsetting, forging, shaping, reduces the cost ofcrankshaft manufacture as the crankshafts can be obtained from plainblanks or bars without resorting to the hitherto customary forging ormachining of spaced enlarged portions.

Another arrangement according to this invention affording a betterutilization of the press tonnage, whether this arrangement is usedseparately or in combination with the preceding one, consists ineliminating the hydraulic ram 9 provided for clamping the lateralholding blocks 14 and 15, and also the hydraulic ram 9' for clamping thelateral holding blocks 16 and 17 illustrated in FIG. 4. According to thearrangement known through the British Pat. No. 622,938, the inclinedslideways 7 and 7' engage, during their downward movement, theregistering inclined slideways of the sliding cradles 3 and 3', thusproducing a horizontal translation of these cradles towards each otherand therefore the upsetting of the crankshaft webs.

As illustrated in FIG. 9, the action exerted by a slideway 7 carried bythe upper cross member upon the registering inclined slideway of thesliding cradle producgs an inclined resultant F of which the horizontalcomponent H provides the horizontal movement of said cradle. On theother hand, its vertical component V is transmitted (see FIG. 4) to thelower bed or worktable 2 of the press, via the sliding cradle 3 andlower frame structure 1 of the forging apparatus. This verticalcomponent having a value of the same order of magnitude as that of thehorizontal component is obviously without any useful function. In thecradle 3 the lower and upper lateral holding blocks 14 and 15respectively are locked in position by means of the ram 9. This ramreacts against the lower face of the upper cross member 5 of theapparatus, which transmits the reaction of the operating thrust directlyto the upper crosshead 6 of the press, thus tending to counteract itsdownward stroke. The same applies to the other sliding cradle 3' and ram9', ofcourse.

If the reactions of rams 9 and 9' are not preponderant in the case ofthe free" forging process described in the British Patent No. 622,938,they become very important in the forging process with fiber orientationaccording to this invention, their sum attaining the order of magnitudeof the maximum thrust required for the metal upsetting.

According to this invention, the rams for clamping the lateral holdingblocks are dispensed with and their action is replaced by the verticalcomponent of the force transmitted via the inclined slideways of theupper cross member to slideways registering therewith, these registeringslideways being however integral with upper holding blocks in lieu ofthe sliding cradles.

This device is illustrated in FIG. 10 showing the forging apparatus inits open position (prior to the forging operation) and also in FIG. 11showing the same apparatus in its closed position (end of forgingoperation). This apparatus comprises a lower frame structure 41supported by the bed or worktable 42 of a conventional forging press; apair of sliding cradles 43 and 43 carried by slideways 44 and 44'provided on said blocks, thus causing the symmetric movement of theseholding blocks towards each other and therefore the upsetting or shapingof the web metal. Adjustable limit stops (not shown) are provided forlimiting the relation to the upper cross member the lowermost positionof each upper lateral die-holding block and consequently their initialrelative distance. The rarns 64 and 64' are provided for pressing theseupper lateral die-holding blocks against said stop at the beginning ofthe forging operation.

The cradles 43 and 43' are also moved apart from their closed positionby the same distances as the upper lateral dieholding blocks and areurged against limit stops (not shown) carried by the lower framestructure 41.

During the closing operation the blank 48 being supported by the lowerdie members the press crosshead 46 is lowered,

, thus carrying along the upper portion A of the apparatus, until framestructure 41; an upper cross member 45 integral with the movablecrosshead 46 of said press (not shown); a pair of upper die holdingblocks 63 and 63' suspended from the cross member 45 by means of a pairof hydraulic rams 64 and of another pair of rams 64', and adapted tomove in relation to said cross member 45 in directions parallel toinclined slideways 47 and 47 due to theprovision of a pair of slideways65 and of another pair of slideways 65. This suspension arrangement isgiven by "way of illustration, not in a limiting sense,-for it willreadily occur to those conversant with the art that variousmodifications may be brought thereto while obtaining the same results.

In the following description the various component elements andfunctions of the apparatus will be designated as explained hereinafter:

a. Upper portion of the apparatus refers to the assembly A including allthe component elements secured to or associated with the uppercrossmember 45;

b. Lower portion of the apparatus refers to the assembly B including allthe component elements secured to or associated with the lower framestructure 41,

c. Closed position" of the apparatus means the position assumed not onlyby the apparatus but by all or any of its component elements at the endof the forging operation;

d. Open position" of the apparatus means the position assumed not onlyby the apparatus but by all or any of its com- "ponent elements beforethe forging operation, with the press crosshead 46 in its uppermostposition.

The Open" and Closed" positions of the apparatus are illustrated inFIGS. 10 and 11 respectively.

Before beginning the forging operation, of course, the apparatus is inits open position. The upper lateral die-holding blocks 63 and 63' areeach moved away from their closed position by a distance equal to theweb upsetting stroke.

As these holding blocks are caused to move parallel to the inclinedslideways 47 and 47' in relation to the upper cross member 45, thissymmetric diverging movement implies, for both die-holding blocks, adownward movement in relation to the cross member 45. It is thisrelative downward movement of the upper lateral die-holding blocks(which takes place under these conditions) that permits during theforging operation proper the relative downward movement ofthe uppercross member in relation to the upper lateral die-holding the upper diemembers 55 and 57 thereof engage the lower die members 54 and 56, thusclamping the blank 48 therebetween. The upper lateral die-holding blocks63 and 63 engage at the same time the sliding cradles 43 and 43', theupper crankpin die 50 engaging on the other hand the lower crankpin die51. Key means (not shown) prevent any relative horizontal movementbetween the cradles 43 and 43', on the one hand, and the die-holdingblocks 63 and 63', respectively. In this position corresponding to thebeginning of the forging operation proper, the thrust exerted by thehydraulic rams 64 and 64' against the die-holding blocks 63 and 63 isamply sufficient to prevent the upperv die members 55 and 57 from beinglifted in relation to the lower lateral die members 54 and 56respectively. As the movable crosshead of the press continues itsdownward stroke when the metal upsetting process is initiated the actionof rams 64 and 64 is suppressed and only the vertical thrust of thepress, which is exerted on the inclined slideways, provides the contactbetween the upper lateral holding blocks and the lower lateral holdingblocks with a pressure sufficient to counteract at any time the openingforce developed by the thrust from the upset metal. The key meansprovided between the upper lateral die-holding blocks 63 and 63' on theone hand and the cradles 43 and 43 on the other hand will cause thesecradles to be driven during the upsetting movement. The other movements,namely the offsetting of the throw and the end of the forging process,take place in the manner described hereinabove, or as in known apparatusaccording to the British Pat. Nos. 622,938, 628,519 and 696,618. Uponcompletion of the forging operation the apparatus is closed so that theupper lateral die members 55 and 57 engage upper crankpin die 50 and thelower lateral die members 54 and 56 engage the lower crankpin die 51.Then the hydraulic rams 64 and 64' are operated in the pull" directionso thatthey withdraw upwards the upper lateral dieholding blocks 63 and63 As a consequence, these blocks are locked in the abutment positionagainst the uppercrankpin die. The movable crosshead 46 of the press israised and thus caused to carry along during its upwards stroke theupper portion of the apparatus; the upper die-holding blocks 63 and 63'are thus disengaged from the cradles 43'and 43 and the lower die members55 and 57 as well as theupper crankpin die 50 are disengaged from theblank 48. Then, it is only necessary to remove the blank 48 from theapparatuswhich, after the movement of the die members away from eachother, is ready to initiate another forging cycle.

The lifting height necessary for extracting the lower portion B of theapparatus from the press table by means of the pull means usuallyassociatedtherewith is definitely inferior to that required forperforming the same operation in the case of known apparatus such asdescribed in the British Pat. No. 622,938. This feature permits ofconstructing for a same press an apparatus capable of forging webs ofgreater dimensions than those permitted by the use of a conventionalforging apparatus.

A The forging with fiber orientation requires upsetting forcesconsiderably greater than those required for the so-called free" forgingprocess; therefore, relatively powerful'and consequently largerauxiliary hydraulic rams 58 must be used in this case. An arrangementcharacterized by a greater compactness than that of the arrangementshown in FIG. 4 consists, as illustrated in FIGS. 10 and 11, inincorporating the hydraulic rams 58 in the sliding cradles 43 (or 43').

With this invention, by using as a power source forging presses of knowndesign and types, the above-described advantageous features can beobtained with crankshaft blanks and similar workpieces havingconsiderably reduced machining allowances and also a continuous grainflow structure which improves very considerably the fatigue strength, orwear and tear resistance, of the parts thus forged.

I claim:

I. An apparatus for forging crankshafts and like workpieces to be fittedto a forging press having a movable crosshead comprising a pair ofcradles mounted to slide horizontally in relation to said press inopposite directions, a cam face on each cradle, a slideway for eachcradle, an -upper cross member having a slideway registering with saidcradle cam face mounted for engagement by said movable crosshead, eachcradle comprising a lateral die member to hold the blank to be forgedduring the forging operation proper and to upset the blank metal as aconsequence of the movement of said cradles towards each other, a lowercrankpin die, an upper crankpin die coacting with said lower crankpindie, said dies during the forging operation clamping the blank andoffsetting the upset metal both transversely and downwardly, a pistonmovable in relation to said upper cross member on which said uppercrankpin die is mounted, a hydraulic ram having its cylinder bodycarried by said cross member controlling said piston, a calibrateddischarge valve set as a function of the dimensions of the workpiece tobe forged for adjusting the pressure developed in said ram for forgingin two stages, namely a first stage comprising upsetting the metal whileoffsetting the crankpin and a second stage comprising forging thecrankshaft webs at the end of said upsetting stage.

2. An apparatus as set forth in claim 1 wherein a pair of dischargevalves are provided to adjust the pressure developed in said cylinder topermit in succession first an upsetting of said blank metal, then afurther upsetting of said blank metal while simultaneously offsettingthe crankpin portion of said blank metal, and then finally upsetting andshaping the webs during the last fraction of the upsetting stage 3.Apparatus as set forth in claim 1 comprising lateral upper dies, upperblocks integral with said lateral upper dies and lower lateral dieslocated in said sliding cradles, the locking of said upper dies uponsaid corresponding lower dies being obtained by means of the verticalcomponent of the force exercised by said upper cross member upon thecorresponding upper block through the intermediary of two inclinedguideways assuring the support of said upper cross member upon said dieholding block, said locking maintaining the blank metal to be forgedupon its pouring between said dies and preventing narrow openings of thelatter during said operation, said upper die holding blocks resting uponsaid sliding cradles and urging them symmetrically towards one anotherin order to produce said pressing back of the blank metal to be forged,additional hydraulic rams for holding said upper die holding blocksagainst abutments at the beginning of the forging operation, means forrendering said rams inoperative when the forging operation begins anddrawing then against said upper die and blockingit there to the end ofthe forging in order'to permit the opening of the apparatus and removalof the forged piece.

1. An apparatus for forging crankshafts and like workpieces to be fittedto a forging press having a movable crosshead comprising a pair ofcradles mounted to slide horizontally in relation to said press inopposite directions, a cam face on each cradle, a slideway for eachcradle, an upper cross member having a slideway registering with saidcradle cam face mounted for engagement by said movable crosshead, eachcradle comprising a lateral die member to hold the blank to be forgedduring the forging operation proper and to upset the blank metal as aconsequence of the movement of said cradles towards each other, a lowercrankpin die, an upper crankpin die coacting with said lower crankpindie, said dies during the forging operation clamping the blank andoffsetting the upset metal both transversely and downwardly, a pistonmovable in relation to said upper cross member on which said uppercrankpin die is mounted, a hydraulic ram having its cylinder bodycarried by said cross member controlling said piston, a calibrateddischarge valve set as a function of the dimensions of the workpiece tobe forged for adjusting the pressure developed in said ram for forgingin two stages, namely a first stage comprising upsetting the metal whileoffsetting the crankpin and a second stage comprising forging thecrankshaft webs at the end of said upsetting stage.
 2. An apparatus asset forth in claim 1 wherein a pair of discharge valves are provided toadjust the pressure developed in said cylinder to permit in successionfirst an upsetting of said blank metal, then a further upsetting of saidblank metal while simultaneously offsetting the crankpin portion of saidblank metal, and then finally upsetting and shaping the webs during thelast fraction of the upsetting stage.
 3. Apparatus as set forth in claim1 comprising lateral upper dies, upper blocks integral with said lateralupper dies and lower lateral dies located in said sliding cradles, thelocking of said upper dies upon said corresponding lower dies beingobtained by means of the vertical component of the force exercised bysaid upper cross member upon the corresponding upper block through theintermediary of two inclined guideways assuring the support of saidupper cross member upon said die holding block, said locking maintainingthe blank metal to be forged upon its pouring between said dies andpreventing narrow openings of the latter during said operation, saidupper die holding blocks resting upon said sliding cradles and urgingthem symmetrically towards one another in order to produce said pressingback of the blank metal to be forged, additional hydraulic rams forholding said upper die holding blocks against abutments at the beginningof the forging operation, means for rendering said rams inoperative whenthe forging operation begins and drawing then against said upper die andblocking it there to the end of the forging in order to permit theopening of the apparatus and removal of the forged piece.